Surface-enhanced Raman Spectral Measurements of 5-Fluorouracil in Saliva

Abstract

The ability of surface-enhanced Raman spectroscopy (SERS) to measure 5-fluorouracil (5-FU) in saliva is presented. The approach is based on the capacity of Raman spectroscopy to provide a unique spectral signature for virtually every chemical, and the ability of SERS to provide μg/mL sensitivity. A simple sampling method, that employed 1-mm glass capillaries filled with silver-doped sol-gels, was developed to isolate 5-FU from potential interfering chemical components of saliva and simultaneously provide SERS-activity. The method involved treating a 1 mL saliva sample with 1 mL of acetic acid, drawing 10 μL of sample into a SERS-active capillary by syringe, and then measuring the SER spectrum. Quality SER spectra were obtained for samples containing as little as 2 μg of 5-FU in 1 mL saliva. The entire process, the acid pretreatment, extraction and spectral measurement, took less than 5 minutes. The SERS of 5-fluorouridine and 5-fluoro-2’-deoxyuridine, two major metabolites of 5-FU, were also measured and shown to have unique spectral peaks. These measurements suggest that disposable SERS-active capillaries could be used to measure 5-FU and metabolite concentrations in chemotherapy patient saliva, thereby providing metabolic data that would allow regulating dosage. Tentative vibrational mode assignments for 5-FU and its metabolites are also given.

Rapid Detection and Identification of Overdose Drugs in Saliva by Surface-Enhanced Raman Scattering Using Fused Gold Colloids

“…This approach is based on the extreme sensitivity of SERS demonstrated by the detection of single molecules [19,20], the ability to measure very small samples (0.1 mL), and the ability to identify molecular structures of drugs through the rich vibrational information provided by Raman spectroscopy [21]. …”

Intracellular SERS Nanoprobes For Distinction Of Different Neuronal Cell Types

“…It utilizes vibrational signatures of bonds in a molecule for their highly sensitive, label-free, nondestructive and noninvasive detection. 24,25 SERS is being used increasingly in biomedical systems for biosensing and detection of target molecules such as recreational drugs, 26 therapeutic substances 27 and metabolites like cancer markers. 28 AuNPs have also been employed as intracellular probes facilitating cancer detection in saliva, 29 blood cells, 30 and tissues.…”

Bioanalytical applications of surface-enhanced Raman spectroscopy: de novo molecular identification

“…130 5-FU was detected in saliva within the physiological range, 1–30 μg/mL. The 5-FU spectrum is dominated by the pyrimidine ring, trigonal ring plus C-F stretching mode, a ring plus C-H waging mode, a ring plus N-H wagging mode, and the symmetric C=O stretch.…”

“…It is suggested that the analytes interact with the metal NPs through the N 3 giving the analyte an upright geometry relative to the NP. 130 …”